Directors Anna Sandilands and Ewan McNicol take us inside the peculiar setting of Uncertain, Texas, a remote town occupied by several eccentric characters whose livelihood rely on the swampy lake that runs through town. When the water is endangered by an infectious plant, it threatens to destroy the fragile ecosystem surrounding it. While technically non-fiction, “Uncertain” presents a cast of characters as compelling as any fiction: The distinctive ensemble includes ex-cons and world-weary fishermen, as well as one extremely committed hog hunter. The filmmakers’ textured approach to documenting the small community is at once a traditional cinema verite portrait and something far stranger — a mysterious look at alienation that feels oddly familiar in spite of its unique surroundings.